Hydrophone



June 5, 1956 w. T. HARRIS 2,749,532

HYDROPHONE Filed June 4, 1952 FIG. 2.

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BY mf-My 2,749,532 Patented June 5, 1956 HYDROPHONE Wilbur T. Harris,Southbury, Conn., assignor to The Harris Transducer Corporation,Woodbury, Conn., a corporation of Connecticut Application .lune 4, 1952,Serial No. 291,706

8 Claims. (Cl. 340-41) My invention relates to acousto-electrictransducers, and in particular to those particularly adaptable tounderwater use.

It is an object to provide an improved device of the characterindicated.

Itis another object to provide an improved hydrophone construction.

It is a general object to meet the above objects with a structurallysimple and rugged construction which may, at the same time, oer superiorperformance characteristics.

Other objects and various other features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification, in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

Fig. 1 is a fragmentary cross-sectional view of a transducerincorporating features of the invention, much of the section beingfragmentary and with exaggerated proportions for purposes of emphasis;

Fig. 2 is a fragmentary View in longitudinal section, illustrating analternative construction;

Fig. 3 is a fragmentary cross-sectional view illustrating a furtheralternative construction; and

Fig. 4 is a longitudinal sectional View illustrating end constructionsfor any of the forms of Figs. l, 2, and 3.

Briefly stated, my invention contemplates a transducer constructionfeaturing simplicity and ruggedness, for particular application tounderwater use. While the construction is basically adaptable to otherforms of radially strictive members, I shall show and describeapplication to toroidally wound, magnetostrictive devices. Superiorperformance is achieved with my construction by providing an internalpressure-release medium affording acoustic softness, yet adequatestructural rigidity. In one form, a wood dowel provides adequatemechanical support while offering acoustic pressure release. In otherforms, similar support is provided by a layer of cork or air-filledrubber or the like, formed as part of a core, as by wrapping such alayer around a metal pipe.

Referring to Fig. 1 of the drawings, my invention is shown inapplication to a transducer comprising a relatively thin-walledradially-strictive cylindrical member 10, carrying means electricallyresponsive to radial deformation thereof. The cylinder 1i) happens to beof magnetostrictive material, such as annealed nickel, and theelectrically responsive means is a winding 11, toroidally enveloping thecylinder 10. For insulation purposes, the winding 11 may be of enameledwire, or the cylinder 1G may be dipped in an insulating plastic beforewinding. As a further precaution, edge insulators, as at 12, may beapplied over the ends of the cylinder 10, prior to winding.

The cylinder is shown to be magnetized by a permanent bar mag-net 13inserted in an elongated slot cut in the periphery of the cylinder 10.The magnet 13 is preferably co-extensive with the cylinder 1Q, and is ofsuch circumferential length L as to support an adequate magnetic flux inthe nickel of cylinder 10. The relative thicknesses of the bar magnet 13and of the cylinder 10 are approximately in inverse ratio of themagnetic permeabilities of these members, so that the properties of auniform toroidally would core are substantially preserved.

In accordance with the invention, I provide pressurerelease means withinthe cylinder 10 in order to effect principal response to pressurefluctuations externally of the cylinder. The pressure-release means maybe a layer of aiI-lled rubber or the like 15, and I have shown layer 15wrapped around a central mechanical support or core 16, which may be ametal pipe. The device may be made rugged and unit-handling by settingthe described parts within a cylindrical boot 17 of rubber-like materialand by filling all radial spaces with a solid sound-transmittingmaterial such as plastic, as indicated at 18-19. The plastic at 18-19should be bubble-free, hard, elastic, and of high strength, and I preferto perform the casting or potting operation under Vacuum conditions.

In Fig. 2, I show a slightly modified construction and at the same timeillustrate the employment of multiple transducer units in a singleassembly. In the construction of Fig. 2, the cylindrical members 20-21may again be magnetostrictive cylinders with permanent-magnet inserts ofthe Fig. l variety, but I illustrate the employment of circumferentiallycontinuous cylinders 24h-21, The cylinders 2li-21 each have their owntoroidal windings 22-23, serially connected or with leads separatelybrought out, depending upon the desired use. As in the case of Fig.l 1,`the windings 22-23 are laid over edge insulators 24 at the ends ofcylinders Ztl- 21. Mechanically rugged, acoustically soft, core supportmay be provided by a central metal tube 25, which may be common to alltransducer elements Ztl- 21, but which I show to be provided separatelyfor each transducer element. The tube or core means 25 may be surroundedwith a layer 26 of pressurerelease material, such as cork, impregnatedcardboard, or the like, and these parts may be made integral with eachcylinder 20-21 by casting with layers of plastic or potting compound2728. For purposes of assembly, the bores of the core tubes 25 for thevarious transducer units Ztl-21 may all be supported on a throughtie-bolt 29 and placed within a rubber-like cover or boot 30 for finalpotting, as with' a sound-transmitting plastic 31. When the plastic 31has set, the tie-bolt 29 may be removed so that the central passage mayremain open for accommodation of such wires and other structure membersas may be necessary for further assembly.

In Fig. 3, I illustrate an alternative core construction providing amechanical support that is also acoustically soft. The core in Fig. 3 ismerely a wood dowel 35, which, again, may be cast to the wound cylinder36 by means of a sound-transmitting potting material 37. The entireassembly is shown potted within a rubber boot 38.

In Fig. 4, l illustrate a manner of making end connections for any ofthe above-described devices. When casting the assembled transducer unitwith its core and Within the protecting cover or boot 40, room should beleft at both ends for accommodation of a closure bushing, as in the caseof bushing 41, which may be of rubber and vulcanized to the jacket of alead cable 42. Leads 45 from the cable 42 are preferably soldered to theleads from the transducer 43 before bushing 41 is inserted in boot 40.This will mean that, upon inserting the bushing 41 in the unlled end ofthe cover 41], the leads 45 will be doubled over, due to their excessivelength. If the core is a wood dowel, as in Fig. 3, this end of the dowelmay be bored out, but in Fig. 4 I show the metal-tube core constructionwhich provides adequate space in which to accommodate the doubled-overlengths of leads 45. After the bushing 41 has been secured, the interiorof the core 46 may be filled with plastic, or left unfilled, as desired;but I have shown that rugged insulated connections may be maintained bypotting the lead end of the interior, as at 48. The other end of thetransducer may be closed by sealing with a plug 47, which may bevulcanized or cemented to the boot 40 and to the potted transducerassembly.

It will be seen that I have described basically simple transducerconstructions featuring ruggedness and improved performance. Myconstructions lend themselves t'o employment under extreme pressureconditions, as at great water depths, because the interior providesstrong mechanical support. At the same time the pressure release aiordedby the core construction renders the transducer responsive substantiallyonly to pressure variations originating outside the transducer.

While I have described my invention in detail for the preferred formsshown, it will be understood that modifications may be made within thescope of the invention as dened in the claims which follow.

I claim:

l. In a transducer of the character indicated, an elongated cylindricalradially strictive member, means electrically responsive to radialdeformations of said member,

a cylindrical metal supporting core within said member,

a pressure-release layer continuously surrounding said core forsubstantially the longitudinal extent of said strictive member, and apotting of hard sound-transmitting material intimately encasing andcontacting said strictive member and the full outer surface of saidpressure-release layer.

2. A transducer according to claim l, in which said pressure-releaselayer is of cardboard.

3. A transducer according to claim 1, in which said pressure-releaselayer is of cork.

4A A device according to claim 1, and including a rubber-like bootencasing said potting and in intimate sound-transmitting relationtherewith.

5. A hydrophone, comprising an elongated cylinder of magnetostrictivematerial, a toroidal winding enveloping said cylinder, apressure-releasing and mechanically supporting core within said woundcylinder, said core being at least longitudinally coextensive with saidcylinder, and a solid and hard intimate bond between said core and saidcylinder for the longitudinal extent thereof.

6. A hydrophone according to claim 5, in which an elongated permanentmagnet is fitted between split longitudinally extending edges of saidcylinder, said bond being intimate to the otherwise exposed surfaces ofsaid permanent magnet.

7. In a transducer of the character indicated, an elongated cylindricalradially strictive member, means electrically responsive to radialdeformations of said member, a Wood dowel within said cylinder and atleast longitudinally coextensive with said cylinder, and a potting ofhard sound-transmitting material intimately encasing and contacting saidstrictive member and the full outer surface of said dowel for at leastthe longitudinal extent of said strictive member.

8. In a transducer of the character indicated, an elongated cylindricalradially strictive member, means electrically responsive to radialdeformations of said member, a pressure-releasing and mechanicallysupporting core within said cylinder and at least longitudinallycoextensive with said cylinder, lead-in means including a sheathed cablewith lead-wire connections to said electrically responsive means at oneend of said cylinder, and a solid and hard intimate bond between saidcore and said cylinder for the longitudinal extent thereof, said bondsolidly covering said end of said cylinder and encasing said leadwireconnection and in sealed relation with said cable sheath.

References Cited in the le of this patent UNITED STATES PATENTS2,076,330 Wood Apr. 6, 1937 2,431,026 Bundy Nov. 18, 1947 2,438,925Krantz Apr. 6, 1948 2,472,388 Thuras June 7, 1949 2,521,136 Thuras Sept.5, 1950 2,613,261 Massa Oct. 7, 1952

